Silencer



Patented Apr. 29, 1930 UNITED STATES PATENT OFFICE ROLAND B. BOURNE, OFHARTFORD, CONNECTICUT, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO THE MAXIMSILENCEB COMPANY, OF HARTFORD, CONNECTICUT, A.

CORPORATION OF CONNECTICUT SILENCER Application filed July 22,

This invention relates to devices for freely conducting a gaseousmedium, or carrier of pressure pulsations such as are concerned withsound waves, to or from the apparatus at which said pulsations originateand at the same time limiting the transmission of said wave ulsationstherethrough. More par ticular y, it refers to silencers which aredesigned for explosive engines, and for the exhaust or intake of airpumps, blowers, air

- channels in the formof curved or spiral passageways, sidebranches,successively disposed along the length of the passageways; thesesidebranches being in the form of chambers acoustically connected withthe passageways and so disposed as to contribute to the silencing of thenoises and the attenuating of the pulsations or vibrations of theexhaust or the intake of the apparatus to which the silencer isconnected, without excessive back pressure. Further objects andadvantages will appear and be readily appreciated rom the detaileddescription of the invention, and the operation of same which follows,taken in connection with the .accompanyingdrawings which show anembodiment of the invention.

Referring to the drawings:

Fig. 1 is a transverse sectional view of a silencertaken along the lineBB of Fig. 2;

Fig. 2 is a longitudinal sectional view-taken along the line A'A of Fig.1; and

Fig. 3 is an isometric view of the silencer with the header membersremoved and with parts of the channel wall broken away.

Referring more particularly to the drawings, 1 and 2 indicate headermembers consisting of circular plates abutting the ends of the silencingunit proper, generally indicated at 1927. Serial No. 207,787.

3. The header members 1 and 2 are provided with suitable inwardl turnedflanges 4 for. fitting over the ends 0? the exterior casing of thesilencing unit 3 and the header member 1 is also provided with a central0 ening 5 which may be either the inlet or outlet of the silencer,depending on whether the silencer is attached to an apparatus which isexhausting or intaking. An outwardly extending flange 6 may be fitted onthe header 1 in any suitable manner to serve as a pi e connection to theapparatus to be silence The silencing unit 3 as a whole is formed as acylindrical-like casing enclosing an interior chamber 7 and in saidcasing there is provided a sin le, long and wide, but relatively shallow(f 1y from-the interior chamber 7 to the exterior of said casing. Thisdevice is not necessarily limited to the use of a wideshallow'pa'ssageway or channel, although such passageways,

epth passage 8 leading SP by virtue of their large surface, afiord ameans for efiectivelyutilizing the viscosity of the medium adjacent tothe bounding sur faces of such passageways in attenuatin alternationsorvibrations of relatively high fregueneies, which might otherwise passunhin ered therethrough. The communica tion of said passage 8 with theoutside is affirded by outlets 9 (as indicated in Figs. 1 and 3) inthe'outer shell of said casing. Y

o Through the said spiral passage 8 both the flow of gas or air andalternations of pressure therein are conducted on the way from the inlet5; :of' said casing to the outlets 9 thereof. The passage 8 will ermit asubstantially un-' impeded travel of t e gaseous medium therethrough,such as a stream of exhaust gas from going to a pump. As regards itsfunction as an explosive engine or the air coming from or an acousticchannel, however, said spiral passage 8 is modified in certain importantparticulars with a view to greatly reducing the amplitude of thepressure alternations trans-. mitted therethrough, whereby substantiallyno noise will be delivered from said silencer. The behaviorcharacteristics of an acoustic system depend on the acoustic reactanceand resistance of its elements and the dis osition of these elementswith relation toeac other.

The modification of the acoustic channel 8 involves the use of acousticelements in a manner which is analogous, within the limitations of theart, to the employment of inductance, capacitance, and resistance in theconstruction of electrical filter networks.

For an example of such an arrangement in the electrical art, referenceis made to the U. S.

patent to Campbell, No. 1,227,113 of May 22, 1917. The acoustic elementsof the passage or channel 8 are the "channel itself, a series of closedchambers 10, distributed lengthwise of said channel 8 and laterallydisposed thereto and various combinations thereof and therebetween. Saidchambers 10, in the disposition shown are substantially closed exceptfor certain openings 11 therefrom into the channel 8. The chambers 10maybe regarded as acoustic elements in shunt with the acoustic ,channel8 and are generally termed acoustic side branches. The number anddimensions of the side branches or chambers 10, and their dispositionalong the channel, as well as the size and number of the communicatingorifices 11, together with the shape and dimensions of the channel 8,will determine the effectiveness thereof in limitin the transmission ofalternations of certain requencies.

In addition to the side branches 10, the channel 8 is further modifiedalong its length by being periodically enlarged and contracted in width.This modification is not always necessary, but in some cases may bedesirable in that such changes in the acoustic channel may provide theproper relation between the parts of said channel or between theelements of said channel and side branches, whereby the functioning ofthe acoustic system as a whole is made more effective. The peripheraldistance between such enlargements is not necessaril uniform.

A preferre method of forming the acoustic or conducting channel 8 withits side branches and periodic enlargements is as follows: Two long andwide sheets 12 and 13 spaced in relatively close parallel relation arecoiled in the form of a spiral (as shown in Fig. 1). Preferably theradial space between the successive convolutions of said spiral (whichprovides the depth for the chambers 10) is greater than the spacebetween the sheets 12 and 13 (which is the depth of the channel 8). Theinnerends 'of said sheets 12 and 13 ay be conterminous, but the outerends thereof do not terminate at the same radial line. Sheet 13, at itsouter portion, is preferably continued beyond the end of sheet 12 for anadditional coil and is then overlapped upon itself and fastened at 14 tocomplete the outside cylindrical casing of said silencer and to form aterminal chamber 19 for the channel 8.

The space between the sheets 12 and 13 forming the channel 8 is providedby channel spacing bars 15. The space between successive convolutions ofsaid pair of sheets is h vided by chamber spacing. bars 16. spacing barsare preferably d s versely of the sheets at four di erent points aroundthe circumference of the casing and those in the same radial line may beheld together and held to said sheets by suitable tie bolts 17 In thismanner, the entire assembly of sheets and spacing bars is held togetheras a unit and in the form described. The headers 1 and 2 abut themarginal edges of the sheets and may be fastened to the ends of saidunit by suitable screw bolts '20.

The channel spacers 15 (as shown in Fig. 2) extend only part way fromthe marginal edges of the sheets 12 and- 13 toward the center thereofand provide the spaces 18, as shown in Fig. 2. The innermost one of suchspacers serves as an entrance to the channel 8 from the chamber 7.Throughout the length of channel 8, (as will be clear from Fig. 1), thechannel spacers 15 will at in-.

tervals restrict the width of said channel 8 to that of the space 18.The portions'of said channel 8 in which said spacers 15 do not occur,have a width of the entire length of the casing 3, between the headers 1and 2. The chamber spacers 16 (as shown in Fig. 2) extend continuouslyacross the entire width of the sheets 12 and 13 from margin to marginthereof and therefore completely block off each end of the side chambers10, whereby said chambers 10 are substantially closed as previouslydescribed. The outer end of the channel 8 opens into or terminates inthe chamber 19 which chamber is open to the outside through theapertures 9. Beyond the osed transterminal chamber 19 and formed by thecon- 18' from Fig. 2) is narrower than the other sim' ar spaces 18 andthat the spacers 15 are correspondingly longer than the spacers 15.Considerable dissipation may be expected in the terminal chamber 20 dueto its shape.

In operation, the silencer will be connected by the flange 6 to thesource of the objectionable noise, which may be the inlet of some t pesof apparatus or the outlet of others. ssuming an exhaust gas of anexplosive engine enters at 5, it will leave the central chamber 7through the entrance 18 and follow a smooth course out through thespiral passage 8 to the terminal chamber 19, and thence through theopenings 9 to the outside. Except for a slight eddying efiect on thecurrent in passing the spacers 15, this out- Ward flow of gas will berelatively unchecked and substantially no back pressure will be causedat the exhaust port of said engine. The sound waves, on the other hand,will be so attenuated in passing through the system as to be scarcelyaudible when emerging from the outlets 9.

Obviously, the design and arrangement of the specific apparatus shownand described can be varied Within the scope of the invention ashereinafter claimed.

What I claim is:

1. A device for conducting a flow of gas to or from an apparatus andlimitin the transmission of wave pulsations tierethrough, comprising aspirally disposed conducting channel and a series of adjacent chamberslaterally disposed with respect thereto, said chambers beingacoustically coupled to said channel.

2. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of wave pulsations therethrough, comprising aspirally disposed conducting channel, relatively extensive in length butsmall in depth and a series of adjacent chambers laterally disposed withrespectthereto, said chambers being acoustically coupled to saidchannel.

3. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of wave pulsations therethrough, comprising aspirally disposed conducting channel, and a series of adjacent chambersof different sizes, laterally disposed with respect thereto, saidchambers being acoustically coupled to said channel.

4. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of wave pulsations there through, comprising aspirally disposed conducting channel. relatively extensive in length butsmall in depth, and a series of adjacent chambers of different sizeslaterally disposed with respect thereto, said chambers beingacoustically coupled to said channel.

5. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of wave pulsations therethrough, comprising aspirally disposed conducting channel, a series of adjacent chamberslaterally disposed with respect thereto, said chambers beingacoustically coupled to said channel and said channel terminating in achamber.

6. A device for conducting a flow of gas.

to or from an apparatus and limiting the transmission of. wavepulsations therethrough, comprising a spirally disposed conductingchannel, a series of ad acent chambers laterally-disposed with respectthereto,

said chambers being acoustically coupled to said channel and a terminalstructure for said channel comprising a chamber arranged for dissipatingacoustic energy.

area with respect to the length thereof, and Y a series of adjacentchambers laterally disposed with respect thereto, said chambers beingacoustically coupled to said channel.

8. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of Wave pulsations therethrough, comprising aspirally disposed conducting channel, said channel being alternatelyenlarged and contracted throughout its length and a series of adjacentchambers laterally disposed with respect thereto, said chambers beingacoustically coupled to said channel.

9. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of wave pulsations therethrough, comprising aspirally disposed conducting chaiinel relatively extensive in length butsma l in depth and having the width thereof alternately enlarged andcontracted in the direction of its length and a series of adjacentchambers laterally disposed with respect thereto, said chambers beingacoustically coupled to said channel.

10. A device for conducting a flow of gas to or from an apparatus andlimiting the trans mission of wave pulsations therethrough, comprising aspirally disposed conducting channel, said channel along its lengthbeing alternately enlarged and contracted in width, a series of adjacentchambers laterally-disposed with respect thereto, said chambers beingacoustically coupled to said channel and a terminal structure for saidchannel comprising a chamber arranged for the dissipation of acousticenergy.

11. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of Wave pulsations therethrough, comprising aspirally disposed conducting channel relatively extensive in length butsmall in depth and along its length being al- .ternately enlarged andcontracted in width,

a series of adjacent chambers laterally disposed with respect thereto,said chambers being of difierent size and acoustically coupled to saidchannel, and a terminal structure for said channel comprising a chamberarranged for dissipating acoustic energy.

12. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of wave pulsations therethrough, comprising aspirally disposed conducting channel and a series of adjacent chamberslaterally disposed with respect thereto, said chambers being closedexcept for one or more relatively small ports opening into said channel.

13. A device for conducting a flow of gas to or from an apparatus andlimiting the trans mission of wave pulsations therethrough, comprising acylindrical-like casing formed from a pair of sheets coiled togetherabout the axis of said casing in the form of a s iral, the marginaledges of said sheets eing abutted by headers at each end of said casing,spacers disposed transversely of said sheets and located at intervals inthe length thereof, certain of said spacers being between said sheets toprovide with said sheets a conditcting channel, and others of saidspacers being between convolutions of said spiral to provide with saidsheets substantially closed chambers laterally disposed with respect tosaid conductingv channel, said chambers being acoustically coupled tosaid channel.

14. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of wave pulsations therethrough, comprising acylindrical-like casing formed from a pair of sheets coiled togetherabout the axis of said casing in the form of a spiral, the marginaledges of said sheets being abutted by headers on at each end of saidcasing, spacers disposed transversely of said sheets and located atintervals in the length thereof, certain of said spacers being betweensaid sheets to provide with said sheets a conducting channel, others ofsaid spacers being between convolutions of said spiral to provide withsaid sheets substantially closed chambers laterally disposed withrespect to said channel, said chambers being'acoustically coupled tosaid channel, and radially disposed members for securing said sheets andspacers together.

15. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of Wave pulsations therethrough, comprising acylindrical-like casing formed from a pair of sheets coiled togetherabout the axis of said casing in the form of a spiral, the marginaledges of said sheets being abutted by headers, one at each end of saidcasing, spacers disposed transversely of said sheets and located atintervals along the length thereof, certain of said spacers beingbetween said sheets to provide with said sheets a conducting channel andextending part way from the marginal edges of said sheets towards thecenter thereof to periodically restrict the width of said channel,others of said spacers being between con-- volutions of said spiral andextending from margin to margin of said sheets to provide with saidsheets chambers laterally disposed with respect to said conductingchannel, said chambers being acoustically coupled to said channel.

16. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of ,Wave pulsations therethrough, comprising acylindrical-like casing formed from a pair of sheets coiled togetherabout the axis of said casing in the form of a spiral, one of saidsheets being extended in such a manner as to finally overlap itself toform a terminal chamber, the marginal edges of said sheets being abuttedby headers, one at each end of said casing, spacers transverselydisposed of said sheets and located at intervals along the lengththereof, certain of said spacers being between said sheets to providewith said sheets a conducting channel and extending part way from themarginal edgesof said sheets toward-the center thereof to periodicallyrestrict the width of said channel, other of said spacers being betweenconvolutions of said spiral and extending from margin to margin of saidsheets to provide with said sheets chambers laterally disposed withrespect to said conducting channel, said chambers being acousticallycoupled to said channel.

17. A device for conducting a flow of gas to or from an apparatus andlimitin the transmission of wave pulsations t erethrough, comprising acontinuously winding conducting channel and a series of chamberslaterally disposed with respect thereto, said chambers beingacoustically coupled to said channel.

18. A device for conducting a flow of gas to or from an apparatus andlimiting the trans mission of Wave pulsations therethrough, comprising acontinuously winding conducting channel and a series of closed chambersof different sizes, laterally disposed with respect to and acousticallycoupled to said channel. v V

19. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of wave pulsations therethrough, comprising acontinuously Winding conducting channel, a series of closed chamberslaterally disposed with-respect to and acoustically coupled to saidchannel, and a terminal structure presenting a terminating acousticimpedance for the system comprising the channel and chambers.

20. A device for conducting a flow of gas to or from an apparatus andlimiting the transmission of Wave pulsations therethrough, comprising acontinuously Winding conducting channel, a series of closed chambers ofdifferent sizes laterally disposed with respect to and acousticallycoupled to said channel, and a terminal structure presenting aterminating acoustic impedance for the system comprising the channel andchambers.

21. A device for conducting a flow of gas to or from an. apparatus andlimiting the transmission of wave pulsations therethrough, comprising acontinuously winding conducting channel, a plurality of acousticelements acoustically coupled to the channel at intervals alon itslength, and a terminal struetum into whlch the channel leads, saidterminal structure presenting a-terminating acoustie impedance for thesystem comprismg the 5 channel and the aeoust1c elements. I

In testimony whereof I have aflixcd my,

signature.

' ROLAND B. BOURKE.

